Radio communication scheme for providing multimedia broadcast and multicast services (MBMS)

ABSTRACT

A radio communication scheme applicable to UMTS providing packet data services, such as multimedia broadcast and multicast services (MBMS), to one or more users by modifying (augmenting) certain existing radio communication protocols while employing a new transport channel (a point-to-multipoint DSCH), and/or by establishing new physical downlink shared channels (C-PDSCH and D-PDSCH). An RLC layer is provided in a single CRNC so that the same MBMS can be transmitted to a plurality of terminals via a point-to-multipoint DSCH, without having to repetitively provide many RLC layers in many SRNCs. Alternatively, a C-PDSCH (physical downlink shared channel for control) and a D-PDSCH (physical downlink shared channel for data) are established to allow periodic transmission of MBMS, permitting users to simultaneously access one or more MBMS.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.11/945,185, filed on Nov. 26, 2007, currently pending, which is acontinuation of U.S. application Ser. No. 10/668,632, filed on Sep. 23,2003, now U.S. Pat. No. 7,623,483, issued on Nov. 24, 2009, whichpursuant to 35 U.S.C. §119, claims the benefit of earlier filing dateand right of priority to Korean patent application No. 10-2002-57499,filed on Sep. 23, 2002, and Korean patent application No. 10-2002-68922,filed on Nov. 7, 2002, the contents of which are all hereby incorporatedby reference herein in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to providing radio (wireless or mobile)data services, such as multimedia broadcast and multicast services(MBMS), in a radio (wireless or mobile) communication system, such as auniversal mobile telecommunication system (UMTS), which is theEuropean-type IMT-2000 system. MBMS can be provided to a plurality ofusers by modifying an existing transport channel (i.e., modify DSCH intoa point-to-multipoint DSCH), and/or by establishing two new physicaldownlink shared channels (i.e., C-PDSCH and D-PDSCH).

2. Description of the Related Art

A universal mobile telecommunication system (UMTS) is a third generationmobile communication system that has evolved from a European standardknown as Global System for Mobile communications (GSM), which aims toprovide an improved mobile communication service based upon a GSM corenetwork and wideband code division multiple access (W-CDMA) wirelessconnection technology.

In December 1998, the ETSI of Europe, the ARIB/TTC of Japan, the T1 ofthe United States, and the TTA of Korea formed the Third GenerationPartnership Project (3GPP), which is currently creating a detailedspecification for standardizing the UMTS.

The work towards standardizing the UMTS performed by the 3GPP hasresulted in the formation of five technical specification groups (TSG),each of which is directed to forming network elements having independentoperations. More specifically, each TSG develops, approves, and managesa standard specification in a related region. Among them, a radio accessnetwork (RAN) group (TSG-RAN) develops a specification for the function,items desired, and interface of a UMTS terrestrial radio access network(UTRAN), which is a new RAN (i.e., radio interface) for supporting aW-CDMA access technology in the UMTS.

I. Features of a UTRAN

The constituting elements of a UTRAN are: radio network controllers(RNCs), Node-Bs and user equipment (UE), such as a terminal. The RNCsenable autonomous radio resource management (RRM) by the UTRAN. TheNode-B is based on the same principles as the GSM base station, being aphysical element performing radio transmission/reception with cells. TheUMTS UE is based on the same principles as the GSM mobile station (MS).

FIG. 1 depicts the components of a typical UMTS, whereby the UMTSgenerally comprises, among many other components, user equipment (UE)such as a terminal 10, a UTRAN 100 and a core network (CN) 200. The UMTSuses the same core network as that of general packet radio service(GPRS), but uses entirely new radio interfaces.

The UTRAN 100 includes one or more radio network sub-systems (RNS) 110,120. Each RNS 110, 120 includes a radio network controller (RNC) 111,121and one or more Node-Bs 112, 113, 122, 123 managed by the RNCs 111,121.

The RNCs 111,121 perform functions such as assigning and managing radioresources, and operate as an access point with respect to the corenetwork 200.

The Node-Bs 112, 113, 122, 123, which are managed by the RNCs 111,121,receive information sent by the physical layer of a terminal 10 (e.g.,mobile station, user equipment and/or subscriber unit) through an uplink(UL: from terminal to network), and transmit data to a terminal 10through a downlink (DL: from network to terminal). The Node-Bs 112, 113,122, 123 thus operate as access points of the UTRAN 100 for the terminal10.

The core network 200 comprises, among other elements, a mobile switchingcenter (MSC) 210 for supporting circuit exchange services, a gatewaymobile switching center (GMSC) 220 for managing connections with othercircuit switched networks, a serving GPRS support node (SGSN) 230 forsupporting packet exchange services, and a gateway GPRS support node(GGSN) 240 for managing connections with other packet switched networks.

A primary function of the UTRAN 100 is to establish and maintain a radioaccess bearer (RAB) for a call connection between the terminal 10 andthe core network 200. The core network 200 applies end-to-end quality ofservice (QoS) requirements to the RAB, and the RAB supports the QoSrequirements established by the core network 200. Accordingly, the UTRAN100 can satisfy the end-to-end QoS requirements by establishing andmaintaining the RAB.

The RAB service can be further divided into lower conceptual levels,namely, into an Iu bearer service and a radio bearer service. The Iubearer service handles reliable user data transmissions between boundarynodes of the UTRAN 100 and the core network 200, while the radio bearerservice handles reliable user data transmissions between the terminal 10and the UTRAN 100.

The data service provided to a particular terminal 10 is divided intocircuit switched (circuit exchanged) service and packet switched (packetexchanged) service. For example, typical voice telephone service fallsunder circuit switched service, while web-browsing service via anInternet connection is classified as packet switched service.

To support circuit switched service, the RNC 111,121 connects with theMSC 210 of the core network 200, and the MSC 210 connects with the GMSC220 that manages connections coming from or going out to other networks.

For packet switched service, the SGSN 230 and the GGSN 240 of the corenetwork 200 provide appropriate services. For example, the SGSN 230supports the packet communication going to the RNC 111,121, and the GGSN240 manages the connection to other packet switched networks, such as anInternet network.

II. Various UTRAN interfaces

Between various network structure elements, there exists an interfacethat allows data to be exchanged for communication therebetween. Theinterface between the RNC 111,121 and the core network 200 is defined asthe Iu interface. The Iu interface is referred to as “Iu-PS” ifconnected with the packet switched domain, and referred to as “Iu-CS” ifconnected with the circuit switched domain.

Various types of identifiers are required to maintain proper connectionsbetween the terminals 10 and the network (UTRAN 100 and core network200). A description regarding a radio network temporary identifier(RNTI) will be made herebelow. The RNTI uses identification(discrimination) data of the terminal 10 while a connection between theterminal 10 and the UTRAN 100 is maintained. To do so, four types ofRNTI, namely, a serving RNC RNTI (S-RNTI), a drift RNC RNTI (D-RNTI), acell RNTI (C-RNTI), and a UTRAN RNTI (U-RNTI) are defined and used.

The S-RNTI is allocated by a servicing RNC (SRNC) when a connectionbetween the terminal 10 and the UTRAN 100 is established, and thisbecomes the data that allows discernment of the corresponding terminal10 by the SRNC. The D-RNTI is allocated by a drift RNC (DRNC) whenhandovers between RNCs 111,121 occur in accordance with the movement ofthe terminal 10. The C-RNTI is the data that allows discernment of aterminal 10 within the controlling RNC (CRNC), and a terminal 10 isallocated a new C-RNTI value from the CRNC whenever the terminal 10enters a new cell. Finally, the U-RNTI comprises an SRNC identity and anS-RNTI, and because the SRNC manages the terminal 10 and becausediscernment data of a terminal 10 within the corresponding SRNC can beknown, the U-RNTI can thus be considered to provide the absolutediscernment data of a terminal 10.

When transmitting data using a common transport channel, a C-RNTI or aU-RNTI is included in the header of the medium access control (MAC)protocol data unit (MAC PDU) at the MAC-c/sh layer. At this time, a UEidentification (ID) type indicator, indicating the type of RNTI that wasincluded, is also included together in the header of the MAC PDU.

For UMTS Terrestrial Radio Access (UTRA), there are typically two typesof physical layer signaling methods, namely, TDD (Time-Division Duplex)and FDD (Frequency-Division Duplex). The UTRA FDD radio interface hasLogical channels, which are mapped to Transport channels, which areagain mapped to Physical channels. Logical channel to Transport channelconversion happens in the MAC (Medium Access Control) layer, which is alower sub-layer in the Data Link Layer (Layer 2).

In the downlink (DL: from network to terminal), three different types ofTransport channels are typically available for data packet transmission,namely the DCH (Dedicated CHannel), the DSCH (Downlink Shared CHannel)and the FACH (Forward Access CHannel).

The DCHs are assigned to single users through set-up and tear downprocedures and are subject to closed loop power control that, if usedfor circuit service such as voice, stabilizes the BER (bit error rate)and optimizes CDMA performance.

The DSCH is a shared channel on which several users can be timemultiplexed. No set-up and tear down procedures are required and thephysical channel on which the DSCH is mapped does not carry powercontrol signaling. However, since closed loop power control is stillrequired, users that are allowed to access DSCH services must have anassociated DCH that is active. The DCH, if not already active due toanother transport service, must be activated just to allow the access tothe DSCH and to carry physical layer signaling only.

The FACH is shared by several users to transmit short bursts of data,but, unlike the DSCH, no closed-loop power control is exerted and noassociated DCH must be activated to access this channel.

For each one of the above channels, different combinations of spreadingfactor (SF) and code rate can provide the bandwidth and the protectionrequired for different data services and communication environments.

III. UTRAN Protocol Structure

FIG. 2 illustrates a radio access interface protocol structure betweenthe terminal 10 and UTRAN 100 that is based upon the 3GPP wirelessaccess network standards. Here, the radio access interface protocol hashorizontal layers including a physical layer, a data link layer and anetwork layer, and has a user plane for transmitting data informationand a control plane for transmitting control signals arrangedvertically.

The user plane is a region to which traffic information of a user, suchas voice or an Internet-protocol (IP) packet, is transmitted. Thecontrol plane is a region to which control information, such as aninterface of a network or maintenance and management of a call, istransmitted.

In FIG. 2, protocol layers can be divided into a first layer (L1), asecond layer (L2) and a third layer (L3) based upon the three lowerlayers of an open system interconnection (OSI) standard model that iswell-known in the art of communication systems. Each layer shown in FIG.2 will now be described.

The first layer (L1) uses various radio transmission techniques toprovide information transfer service to the upper layers. The firstlayer (L1) is connected via a transport channel to a MAC (medium accesscontrol) layer located at a higher level (precedence), and the databetween the MAC layer and the physical layer is transferred via thistransport channel.

Data is transmitted according to a transmission time interval (TTI)through the transport channel. The physical channel transfers data upondivision into certain units of time, called frames. In order tosynchronize the transport channel between the UE (terminal 10) and theUTRAN 100, a connection frame number (CFN) is used. For the transportchannels, with the exception of the paging channel, the range of the CFNvalue is between 0 to 255. That is, the CFN is repeated (circulated) bya period of 256 frames.

Besides the CFN, a system frame number (SFN) is also used to synchronizethe physical channel. The SFN value has a range of 0 to 4095 and is thusrepeated (circulated) by a period of 4096 frames.

The MAC layer provides a re-allocation service of MAC parameters forallocation and re-allocation of radio (wireless) resources. The MAClayer is connected to an upper layer called a RLC (radio link control)layer through a logical channel, and various logical channels areprovided according to the type of transmitted information. In general,when information of the control plane is transmitted, a control channelis used. When information of the user plane is transmitted, a trafficchannel is used.

The MAC layer is divided into a MAC-b sublayer, a MAC-d sublayer, and aMAC-c/sh sublayer, according to the type of transport channel beingmanaged. The MAC-b sublayer manages a broadcast channel (BCH) handlingthe broadcast of various data and system information.

The MAC-c/sh sublayer manages a shared transport channel, such as aforward access channel (FACH), a downlink shared channel (DSCH), or thelike, that one terminal shares with other terminals. In the UTRAN 100,the MAC-c/sh sublayer is located in a controlling RNC (CRNC) and manageschannels shared by all terminals in a cell, so that one MAC-c/shsublayer exists for each cell. A MAC-c/sh sublayer also exists in eachterminal 10, respectively.

The MAC-d sublayer manages a dedicated channel (DCH), which is adedicated transport channel for a specific terminal 10. Accordingly, theMAC-d sublayer is located in a serving RNC (SRNC) that manages acorresponding terminal 10, and one MAC-d sublayer also exists in eachterminal 10.

A radio link control (RLC) layer provides support for reliable datatransmission, and may perform a function of segmentation andconcatenation of an RLC service data unit (SDU) coming from a higherlayer. The RLC SDU transferred from the higher layer is adjusted in itssize according to a throughput capacity at the RLC layer, to whichheader information is added, and is then transferred to the MAC layer inthe form of a protocol data unit (PDU), i.e., a RLC PDU. The RLC layerincludes an RLC buffer for storing the RLC SDU or the RLC PDU comingfrom the higher layer.

The RLC layer may be part of the user plane or the control plane inaccordance with an upper layer connected thereto. The RLC layer is partof the control plane when data is received from the RRC layer (explainedhereafter), and the RLC layer is part of the user plane in all otherinstances.

A packet data convergence protocol (PDCP) layer is located at an upperlayer from the RLC layer, allowing data to be transmitted effectively ona radio interface with a relatively small bandwidth through a networkprotocol, such as the IPv4 or the IPv6. For this purpose, the PDCP layerperforms the function of reducing unnecessary control information usedin a wired network, and this function is called, header compression.

Various types of header compression techniques, such as RFC2507 andRFC3095 (robust header compression: ROHC), which are defined by anInternet standardization group called the IETF (Internet EngineeringTask Force), can be used. These methods allow transmission of only theabsolutely necessary information required in the header part of a data,and thus transmitting a smaller amount of control information can reducethe overall amount of data to be transmitted.

As can be understood from FIG. 2, in case of the RLC layer and the PDCPlayer, a plurality of entities may exist in a single layer thereof. Thisis because one terminal may have many radio (wireless) carriers, andtypically, only one RLC entity and one PDCP entity is used for eachradio carrier.

A broadcast/multicast control (BMC) layer performs the functions ofscheduling a cell broadcast (CB) message transferred from the corenetwork 200 and of broadcasting the CB message to UEs positioned in aspecific cell or cells. At the UTRAN 100, the CB message transferredfrom the upper layer is combined with information, such as a message ID(identification), a serial number, a coding scheme, etc., andtransferred to the RLC layer in the form of a BMC message and to the MAClayer through a common traffic channel (CTCH), which is a logicalchannel. The logical channel CTCH is mapped to a transport channel(i.e., a forward access channel (FACH)), and to a physical channel(i.e., a secondary common control physical channel (S-CCPCH)).

The radio resource control (RRC) layer located at the lowest portion ofthe third layer (L3) is only defined in the control plane, and controlsthe transport channels and the physical channels in relation to thesetup, the reconfiguration, and the release (cancellation or tear down)of the radio bearers (RBs). Here, the RB refers to a service provided bythe second layer (L2) for data transmission between the terminal 10 andthe UTRAN 100. In general, the set up of the RB refers to the process ofstipulating the characteristics of a protocol layer and a channelrequired for providing a specific data service, and setting therespective detailed parameters and operation methods therefor.

Among the RBs, the RB used for exchanging an RRC message or a NAS(Non-Access Stratum) message between a particular terminal 10 and theUTRAN 100 is called a SRB (Signal Radio Bearer). If a SRB is establishedbetween a particular terminal 10 and the UTRAN 100, an RRC connectionexists between the terminal 10 and the UTRAN 100. A terminal 10 havingan RRC connection is said to be in a RRC connected mode, while aterminal 10 without an RRC connection is said to be in idle mode. Aterminal 10 in an RRC connected mode is classified, depending upon thechannel received, into the states comprising, Cell_PCH or URA_PCH,Cell_FACH, Cell_DCH.

For a terminal 10 in the Cell_DCH state, a dedicated logical channel anda transport channel DCH are established, and the DCH is always received.If a DSCH has been established, the DCH and the DSCH can be receivedtogether. For a terminal 10 in the Cell_FACH state, a dedicated logicalchannel and a transport channel FACH are established, and FACH data canalways be received. In the Cell_FACH state, DCH and DSCH cannot bereceived. For a terminal 10 in the Cell_PCH and URA_PCH states, adedicated logical channel has not been established. However, in thisstate, a paging message via the PCH, or a CBS (cell broadcast service)message via the FACH can be received.

Here, URA (UTRAN Registration Area) is an area defined by one or morecells, and provides an efficient method for supporting the mobility ofthe terminal 10. When a terminal 10 is in the URA_PCH state, the UTRAN100 does not know which cell the corresponding terminal 10 is locatedin, but it can be discovered as to which URA region the terminal 10 islocated in. Thus, when performing paging, a paging message istransmitted to all cells, which are part of a particular URA region. Incontrast, if the terminal 10 is in the Cell_PCH state, because the UTRAN100 can determine the cell that the terminal 10 is located in, pagingmessages are only transmitted to those particular cells having aterminal 10 existing therein.

Next, the downlink shared channel (DSCH) will be described in moredetail. The DSCH is used to carry dedicated control information ortraffic data to a plurality of users who share the channel. Codemultiplexing is performed for the plurality of users so that a singlechannel may be shared. Thus, the DSCH can be defined by a series of codesets.

Unlike in the uplink, the downlink suffers from a code deficiency (i.e.,code shortage) problem. This is because there is a limit on the numberof codes that a cell can have for a single base station (Node-B). Thisis related to a spreading factor (SF), and the number of physicalchannels decreases as the data transmission rate increases. Also,certain types of data services exhibit data burst characteristics. Thus,when only a single channel is allocated continuously, efficient use ofcodes becomes difficult. Namely, if the DCH is used to carry data havingburst characteristics, code shortage problems occur.

To address this problem, a plurality of scrambling codes may be used.However, the use of scrambling codes cannot increase code usageefficiency, and the complexity of the receiving end is undesirablyincreased.

Alternatively, a method of commonly using (i.e., sharing) a singlechannel is used, and to do so, code multiplexing is employed. For thephysical channel, the basic transmission unit is called a radio frame.Code allocation is performed for each and every radio frame. Thus, achannel code for the physical channel of the DSCH is varied for each andevery radio frame.

A physical downlink shared channel (PDSCH), which is a type of physicalchannel, is used to transport a transport channel, i.e., a DSCH. Namely,the PDSCH is used to carry the DSCH, i.e., the PDSCH is mapped to theDSCH. One PDSCH corresponds to one channelization code. One PDSCH radioframe is allocated to only one particular UE (terminal). The radionetwork allocates a respectively different PDSCH to a respectivelydifferent UE for each radio frame. More than one PDSCH, each having thesame SF for a particular radio frame, may be allocated to one particularUE. Each PDSCH is correlated with (i.e., is associated with) onededicated physical channel (DPCH) and operates for each and every radioframe. Such correlated DPCHs are called associated DPCHs.

The PDSCH and the associated DPCH need not have the same SF. The PDSCHcannot transport physical layer control information, such as Pilot(pilot control), TFCI (Transport-Format Combination Indicator), TPC(Transmitter Power Control), thus all physical layer control informationrelated to the DSCH are carried via a downlink physical control channel(DPCCH) that constitutes an associated DPCH. The UE can decode the DSCHby using the TFCI Field 2 (TFCI2) data carried via the associated DPCH.

Macrodiversity is not applied to the DSCH, and the DSCH is transmittedfrom only one particular cell. Here, it is understood that“macrodiversity” refers to enabling a mobile station (UE) to communicatewith the fixed network by more than one radio link, i.e. a mobile (UE)can send/receive information towards/from more than one radio port (orbase station (Node-B)).

UMTS has several different time slot configurations depending upon thechannel being used. In the 3GPP standard, a basic transmission unit ofthe physical channel is a radio frame. The radio frame has a length of10 ms and is comprised of 15 time slots. Each time slot has fields fortransmitting various data bits, such as TFCI. For example, in DPCHdownlink and uplink time slot allocation, each slot may have TCP(Transmit Power Control), FBI (Feedback Information) used for closedloop transmission diversity, TFCI containing information related to datarates, and pilot bits, which are always the same and are used forchannel synchronization.

FIG. 3 illustrates a channel coding method for a TFCI that istransmitted via the associated DPCH. In general, TFCI (which is 10-bitdata) are encoded into 30-bit data through channel coding, andtransmitted via a TFCI field in each and every frame. However, for theDPCH, which is an associate or a counterpart (complement) to the DSCH,TFCI division (partition) mode channel coding is employed as shown inFIG. 3. Here, the 5-bit data at each input terminal refers to a firstTFCI field data and a second TFCI field data, respectively. The firstTFCI field provides the transmission format association data of thetransport channel DCH that is mapped to the DPCH. In contrast, thesecond TFCI field provides the transmission format association data ofthe associated DSCH, and the channel code data. Each of the 5-bit TFCIfield data is encoded into two 16-bit TFCI code words via therespectively different bi-orthogonal code encoders. The data that hasbeen encoded into two 16-bit TFCI code words through channel coding, ismixed together with one TFCI field that constitutes a radio frame andthen arranged (distributed).

FIG. 4 illustrates a protocol model for the DSCH when there is an Iurinterface, which is an interface between the SRNC and the CRNC. On thedownlink, logical channels that are mapped to the DSCH include a DTCH(dedicated traffic channel) that is used to carry data for a particularUE, and a DCCH (dedicated control channel) that is used to carrysignaling data (e.g., RRC messages) for a particular UE. In practicaluse, the DSCH is mainly used for carrying DTCH data. The RLC modes forthe DSCH include an answer mode or a non-answer mode. The DSCH alwaysoperates together with one or more DL DCHs (downlink dedicatedchannels). The DSCH data transmission scheduling is performed by theMAC-c/sh of the CRNC. The DSCH frame protocol (FP), by adding a headerto the MAC-c/sh PDU, creates a DSCH FP PDU that is then transferred tothe base station (Node-B).

The DSCH is allowed to transfer to the corresponding terminals (UE),PDSCH OVSF (orthogonal variable spreading factor) code allocation datathat are performed at the MAC-c/sh, by employing the TFCI codeword ofthe associated DPCCH. This is advantageous in efficiently using radio(wireless) resources, for packet data that have a high peak data ratebut a relatively low activity cycle. The MAC-c/sh of the CRNCtemporarily allocates OVSF (orthogonal variable spreading factor) codesof the PDSCH to the user for each and every frame, whenever packet datatransmissions are requested.

FIG. 5 illustrates a DSCH data transfer procedure used in the DSCH FP ofthe Iub interface, which is an interface between a Node-B and a CRNC.This procedure is used when DSCH data frames are transmitted from theCRNC to the base station (Node-B). The Iub DSCH data stream containsdata that is transmitted on a single DSCH for a single UE. For one UE,one or more Iub DSCH data streams may exist. A single Iub user planetransport bearer transmits only one DSCH data stream. Here, a transportbearer refers to a carrier of a wired network existing within the UTRANthat provides data transmission services between an RNC and a basestation, or between two different RNCs.

IV. Providing MBMS to Users

Multimedia broadcast/multicast service (MBMS) is a service to providemultimedia data (e.g., audio, images, video) to a plurality of terminals(users) by using a uni-directional point-to-multipoint bearer service.MBMS was newly developed because of the shortcomings in the related art3GPP wireless access network standards described above. In particular,the related art techniques for establishing various channels andprotocol execution have certain limitations and disadvantages inproviding multimedia services to users.

For example, employing CBS messages (previously described) isproblematic for the following reasons. First, the maximum length of aCBS message is restricted to 1230 octets. Thus, this is not appropriatefor use in broadcasting or multicasting multimedia data. Second, becausea CBS message is only broadcast to all terminals within a cell, themulticasting of data via a wireless (radio) interface to provide dataservices to only a particular group of users (terminals) is notpossible.

In general, “multicast” refers to transmitting (propagating) data to aspecified group of users connected to a local area network (LAN) or theInternet, whereby one user transmits data to a few users, who each thentransmit the received data to a plurality of users using a bucket relaymethod. Unlike “unicast,” which is the transmission of data to onespecified user, or “broadcast,” which is the transmission of data to anunspecified plurality of users, multicast is the transmission of data toa specified plurality of users.

In UMTS, the multimedia services to be provided to users are based uponpacket switching and Internet access. MBMS refers to a downlinktransmission service for providing data services such as, streaming dataservices (e.g., multimedia, video on demand, webcast) or background dataservices (e.g., e-mail, short message services (SMS), downloading), to aplurality of terminals by employing a common (dedicated or exclusive)downlink channel.

MBMS can be classified into a broadcast mode and a multicast mode. TheMBMS broadcast mode refers to transmitting multimedia data to all userswithin a broadcast area, whereby a broadcast area refers to a regionwhere broadcast service is possible. Within a single PLMN (public landmobile network), which is any wireless communications system intendedfor use by terrestrial subscribers in vehicles or on foot, more than onebroadcast region may exist, and more than one broadcast service may beprovided in one broadcast region. Also, a single broadcast service maybe provided to many broadcast regions. The related art procedures forusers to receive a certain broadcast service are as follows.

(1) Users receive a service announcement provided by the network. Here,a service announcement refers to providing to the terminal, an index andany related information of the services to be provided.

(2) The network establishes a bearer for the corresponding broadcastservice.

(3) Users receive service notification provided by the network. Here,service notification refers to notifying the terminal of the informationregarding the broadcast data to be transmitted.

(4) Users receive the broadcast data transmitted from the network.

(5) The network releases the bearer for the corresponding broadcastservice.

The MBMS multicast mode refers to the service for transmitting multicastdata to a particular user (terminal) group within a multicast area.Here, a multicast area refers to a region where multicast service ispossible. Within a single PLMN, more than one broadcast region mayexist, and more than one broadcast service may be provided in onebroadcast region. Also, a single broadcast service may be provided tomany broadcast regions. The related art procedures for users to receivea certain multicast service are as follows.

(1) A user must first subscribe to a multicast subscription group. Here,subscribing refers to establishing a relationship between the serviceprovider and the user (subscriber). A multicast subscription grouprefers to a group of users who have completed the subscription process.

(2) Users who subscribed to the multicast subscription group receive anetwork announcement provided by the network. Here, a serviceannouncement refers to providing to the terminal, an index and anyrelated information of the services to be provided.

(3) A user who subscribed to a multicast subscription group must join amulticast group in order to receive a particular multicast service.Here, a multicast group refers to a group of users receiving aparticular multicast service. Joining refers to one user merging withthe other users in a multicast group who congregated to receive aparticular multicast service. Joining is also referred to as MBMSmulticast activation. Thus, a user can receive particular multicast datathrough MBMS multicast joining or activation.

(4) The network establishes a bearer for the corresponding multicastservice.

(5) A user who joined a multicast group receives service notificationprovided by the network. Here, service notification refers to notifyingthe terminal of the information regarding the broadcast data to betransmitted.

(6) Users receive the multicast data transmitted from the network.

(7) The network releases the bearer for the corresponding broadcastservice.

MBMS user data (i.e., control information and content data) istransmitted from the RNC 111,121 to the terminal 10 via a base station(Node-B) by employing services of the user plane of the UTRAN protocol.Namely, the services of the PDCP, RLC, and MAC layers in the user plane,and services of the physical plane are employed to transmit the MBMSuser data from the RNC to the terminals (UE) via the base station(Node-B). More particularly, the MBMS user data that is transferred fromthe CN (core network 200) undergoes header compression at the PDCPlayer, and then is transferred to the RLC UM entity via the RLC UM SAP.The RLC UM entity then transfers the data to the MAC layer via a logicalchannel, i.e., a common (shared) traffic channel. The MAC layer adds aMAC header to the received data and transfers the data to the physicallayer in the base station (Node-B) via a common (shared) transportchannel. Finally, after further processing, such as coding andmodulation at the base station (Node-B) physical layer, datatransmission to the terminals via a common (shared) physical channel isperformed.

An MBMS RB, which is a radio bearer (RB) for the MBMS, serves totransmit user data of one specific MBMS, transferred from the corenetwork 200 to the UTRAN 100, to a specific terminal group. The MBMS RBis divided into a point-to-multipoint RB and a point-to-point RB.

In order to provide MBMS, the UTRAN 100 selects one of the two types ofMBMS RBs. In order to select the MBMS RB, the UTRAN 100 recognizes thenumber of users (terminals 10) for the specific MBMS existing in onecell. The UTRAN 100 internally sets a threshold value, and if the numberof users existing in a cell is smaller than the threshold value, theUTRAN 100 sets a point-to-point MBMS RB, whereas if the number of usersexisting in a cell is greater than the threshold value, the UTRAN 100sets a point-to-multipoint MBMS RB.

SUMMARY OF THE INVENTION

One aspect of the invention involves the recognition of the drawbacks,problems, and disadvantages of the related art. Namely, the inventors ofthe present invention recognized certain problems and disadvantagesrelated to transmitting an MBMS service, which provides the same data toa plurality of particular terminals (users), via the DSCH of the relatedart or other channels used for packet data transmissions.

In the related art DSCH, the RLC and MAC-d layers needed fortransmitting user data are all located within the SRNC. Also, thedownlink data of the MAC-d is transferred to the MAC-c/sh of the CRNC.As the DSCH is a channel that is shared by many users, a single DSCHcarries data for a plurality of terminals. The data for each terminal istransferred to a common CRNC from a SRNC (located in Layer 2) requiredfor each terminal. Here, the data of each SRNC are for respectivelydifferent data services, and thus must be transferred to differentcorresponding terminals.

However, when providing MBMS, a plurality of SRNCs for a single terminalgroup, transfer the same data to the CRNC. Thus, a plurality of RLC andMAC-d layers exist within each and every SRNC for transmitting the sameservice data. Furthermore, the same data needs to be transmitted overthe Iur interface, which is undesirably repetitive. As such, theprocessing capabilities of the RNC CPU, the capacity of memory devices,radio (wireless) communication network resources, and the like areundesirably wasted. Such related art problems and disadvantages onlyincrease with the number of multimedia services that need to be providedto the users based upon ever increasing consumer demands.

In order to overcome the problems that may occur when transmitting datavia a related art DSCH, the present invention proposes to provide a RLClayer within the CRNC to allow multicast data via a “point-to-multipointDSCH” (explained below). Here, the data to be transmitted via the DSCHdoes not pass through the MAC-d layer, but is transferred directly fromthe RLC to the MAC-c/sh layer. By transmitting the same service data toa plurality of terminals via the DSCH using this method, the RLCs forthe corresponding service are not repetitively provided in the SRNC, butonly exist only in the CRNC and thus UTRAN resources can be efficientlyused.

The DSCH of the present invention provides point-to-multipoint radiobearer services, and allows transmission of data for a common trafficchannel (such as a CTCH) to a particular terminal group. Namely, theradio (wireless) system establishes a downlink shared channel (DSCH) tomulticast a plurality of services, and a particular multicast service isprovided to only a particular terminal group during a particular radioframe of the DSCH. Here, for the particular terminal group wishing toreceive a multicast service via the DSCH, the radio system establishes aDCH (dedicated channel) for each terminal and provides DSCH controlinformation to each terminal. The DSCH control information includesinformation whether a terminal should receive a particular radio frameof the downlink shared channel, the channel codes used in the PDSCH, thesize of the data to be transmitted in the particular radio frame,decoding data, and the like.

In the present invention, the DSCH providing point-to-multipoint radiobearer services is referred to as a “point-to-multipoint DSCH” todistinguish over the related art DSCH. On the other hand, if the DSCH isused to provide a point-to-point radio bearer service, it is referred toas a “point-to-point DSCH.” Also, in the present invention, a DSCHincludes a high speed downlink shared channel (HS-DSCH) so that a DSCHcan be replaced by a HS-DSCH.

Additionally, in a related art radio (wireless or mobile) communicationsystem employing a common transport channel to provide multimediabroadcast or multicast service (MBMS), the greatest problem in providingvarious types of MBMS to one cell is the fact that the transmissionpower required for one MBMS takes up a large proportion of the overallpower amount used by the base station (i.e., Node-B in UMTS).

Accordingly, when MBMS is provided by the UTRAN, the factor that must beprimarily considered is minimizing the transmission power required forthe particular MBMS in order to maximize the number of data servicesthat can be provided by the base station (Node-B).

When a point-to-multipoint MBMS RB is provided by the related art, acommon transport channel, such as FACH or DSCH, may be used. However,these common transport channels have the following drawbacks andproblems related to not being able to efficiently provide MBMS withrespect to transmission power.

First, the problems associated with providing MBMS via a FACH will beconsidered. In the related art FACH, once a downlink channel code hasbeen set, it cannot be changed or converted on demand. Namely, becausethe spreading factor cannot be varied, discontinuous transmissions (DTX)(i.e., not transmitting data for a prescribed period of time) wereperformed. Although discontinuous transmissions can be applied when theamount of data changes from time to time, doing so is disadvantageousbecause the amount of power required in transmitting data is undesirablyhigh.

Next, problems and disadvantages when providing MBMS via a DSCH will beexplained. In the related art, an associated DPCH must be established(created) so that the DSCH can be used to carry power control and othercontrol information. When transmitting data via a DSCH to a plurality ofterminals, a plurality of associated DPCHs must be created in order toprovide a single data service, such as MBMS. Considering the poweramount requirements for transmitting a plurality of associated DPCHs,providing MBMS through a related art method employing DSCH isinefficient.

Accordingly, an object of the present invention is to provide acommunication scheme for channel code control information in a radio(wireless) communication system. This is achieved by using a newlycreated physical downlink shared channel for data (referred to asD-PDSCH hereinafter) that transmits only data without any physical layercontrol information such as pilot bits and power control bits. TheD-PDSCH employs a variable spreading with orthogonal variable spreadingfactor codes or link adaptation techniques that adaptively controlmodulation and coding according to channel conditions or radioresources.

Also, a newly created physical downlink shared channel for control(referred to as C-PDSCH hereinafter) is employed to carry the controlinformation related with the D-PDSCH, so that the efficiency of datatransmissions for MBMS is improved.

The wireless mobile communication system according to the presentinvention includes a channel structure having a D-PDSCH that supports atleast one multicast service for a plurality of terminals, and a C-PDSCHthat employs a different channel code than that of the D-PDSCH and thatallows multicasting of control information for the multicast service tothe plurality of terminals.

The C-PDSCH allows broadcasting and multicasting of control informationfor respectively different broadcast or multicast services duringrespectively different time periods. Also, the C-PDSCH is for notifyinga particular terminal or terminal group as to whether they shouldreceive data during a prescribed time period of the D-PDSCH.

Control information refers to information that is necessary for aterminal to receive the D-PDSCH (e.g., the channel code numbers or thespreading factor channel code numbers of the D-PDSCH or the like). Also,the control information that is transmitted during a certain time periodof the C-PDSCH, is the control information to be used during a certaintime period of the D-PDSCH, whereby the two time periods have aprescribed time difference (delay) between them. Typically, the timeperiods of the D-PDSCH and the C-PDSCH can be one radio frame. Also, ofthe various corresponding radio frames for the C-PDSCH, specializedfields, such as a TFCI field may be used.

Thus, to achieve these and other advantages and in accordance with thepurpose of the invention, as embodied and broadly described herein, thepresent invention is directed to providing radio (wireless or mobile)data services, such as multimedia broadcast and multicast services(MBMS), in a radio (wireless or mobile) communication system, such as auniversal mobile telecommunication system (UMTS), by modifying(augmenting) certain existing radio communication protocols whileemploying a new transport channel (a point-to-multipoint DSCH), and/orby establishing new physical downlink shared channels (C-PDSCH andD-PDSCH) to substantially obviate one or more problems due tolimitations and disadvantages of the related art.

Additional advantages, objects, and features of the invention will beset forth in part in the description which follows and in part willbecome apparent to those having ordinary skill in the art uponexamination of the following or may be learned from practice of theinvention. The objects and advantages of the invention may be realizedand attained as particularly pointed out in the appended claims.

It is to be understood that both the foregoing general description andthe following detailed description of the present invention areexemplary and explanatory and are intended to provide furtherexplanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this application, illustrate embodiment(s) of the invention andtogether with the description serve to explain the principles of theinvention.

In the drawings:

FIG. 1 illustrates the components of a typical UMTS network applicablein the related art and in the present invention;

FIG. 2 illustrates a radio access interface protocol structure betweenthe terminal and UTRAN that are based upon the 3GPP wireless accessnetwork standards;

FIG. 3 illustrates a channel coding method for a TFCI that istransmitted via the associated DPCH;

FIG. 4 illustrates a signal flow diagram of a data transmission processfor a DSCH via an Iur interface according to the related art;

FIG. 5 illustrates a data transmission process for the DSCH via an Iubinterface according to the related art;

FIG. 6 illustrates a signal flow diagram of a data transmission processfor a point-to-multipoint DSCH via an Iub interface according to anembodiment of the present invention;

FIG. 7 illustrates is state transition diagram when MBMS is provided viaa FACH and a DSCH according to an embodiment of the present invention;

FIG. 8 illustrates a MBMS data transmission process via apoint-to-multipoint DSCH according to an embodiment of the presentinvention.

FIG. 9 illustrates a time slot structure of a D-PDSCH according to anembodiment of the present invention;

FIGS. 10A through 10E illustrate a time slot structure of the C-PDSCHaccording to an embodiment of the present invention;

FIG. 11 illustrates the time relationship between the C-PDSCH and theD-PDSCH according to an embodiment of the present invention;

FIG. 12 illustrates a transmission and reception process of the C-PDSCHand the D-PDSCH according to an embodiment of the present invention;

FIG. 13 illustrates a transmission and reception process of the C-PDSCHand the D-PDSCH according to another embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made in detail to various embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings. Wherever possible, the same reference numbers will be usedthroughout the drawings to refer to the same or like parts.

The present invention can be implemented in a radio (wireless or mobile)communication system such as UMTS (Universal Mobile TelecommunicationSystem) developed by the 3GPP. However, without being restrictedthereto, the present invention can be also applied to or modified toaccommodate other radio (wireless) communication systems operating underdifferent standards.

Also, it should be noted that the present invention is applicable toHSDPA (high-speed downlink packet access) and other concepts that aim toincrease packet data throughput. The following description will focus ona radio access network employing a DSCH merely for exemplary purposes.However, applicability of the present invention to HSDPA techniques isfeasible and understood, because the concepts involved are similar. Forexample, similar to the DSCH, an HS-DSCH is a transport channel carryingthe user data with HSDPA operation.

I. Providing MBMS by Employing a Point-to-Multipoint DSCH

FIG. 6 illustrates a radio protocol structure for a point-to-multipointDSCH according to an embodiment of the present invention. As shown, theCRNC 510 is formed such that when data is transported via apoint-to-multipoint DSCH of the present invention, the data istransferred by the RLC 511 to the MAC-c/sh 512, and the passes throughthe DSCH FP and the TNL, and transported to the base station (Node-B)520, which then transmits to a terminal (UE) 530.

The point-to-multipoint DSCH of the present invention, unlike therelated art DSCH, does not have a corresponding radio protocol entity inthe SRNC. Also, the MAC and RLC entities only exist in the CRNC 510.Here, the RLC can operate in a transparent or non-transparent mode,whereby the non-responsive mode is more preferable.

When data to be transmitted in the multicast service is generated at theCRNC 510, the CRNC RLC layer 511 inserts a non-transparent header forthe received PDCP PDU to form a RLC PDU. This RLC PDU is thentransferred to the CRNC MAC layer 512 via a logical channel. The CRNCMAC layer 512 forms a MAC PDU by inserting a MAC header. The MAC layer512 performs a transmission scheduling based upon the priority of theMAC PDU, forms the necessary DSCH control information, and transfers theMAC PDU and the DSCH control information to the physical layer in thebase station (Node-B) 520 by using the frame protocol layer services.The base station physical layer respectively transmits the DSCH controlinformation to each and every terminal within the terminal group via aDCH, and multicasts the MAC PDU after encoding, to the particularterminal group via the DSCH.

The physical layer 531 of each terminal 530 in the terminal groupreceives the DSCH control information via the DCH, and determineswhether to receive the point-to-multipoint DSCH during a particularradio frame in accordance with the content of the received DSCH controlinformation. If the DSCH control information indicates that thepoint-to-multipoint DSCH should be received, the physical layer 531 ofthe terminal 530 receives the point-to-multipoint DSCH during aparticular radio frame by using the DSCH control information, decodesand then transfers the MAC PDU to the MAC layer 532 in the terminal 530via a transport channel. Then, the terminal MAC layer 532 removes theinserted MAC header of the received MAC PDU, and transfers the RLC PDUto the RLC layer of the terminal. The terminal RLC layer removes theheader from the received RLC PDU and transfers it to the PDCP layer ofthe terminal for processing.

Next, the data transmission process for a point-to-multipoint DSCH thatincludes an Iub region will be explained. The CRNC 510 MAC 512 forms aDSCH transmission block, and transfers it to the DSCH FP layer 513 ofthe RNC. The RNC DSCH FP attaches the DSCH control information to theMAC PDU to form a DSCH data frame, which is then transferred to the TNL(transport network layer) 514. Here, the DSCH control informationincluded in the DSCH data frame comprises PDSCH channel code data thatis determined at the MAC 512 and transmission format association data.The RNC transfers the DSCH data frames to the base station 520 via atransmission bearer provided from the TNL 514. Here, the transmissionbearer of the Iub transmits only the data for a particular MBMS. Thus,for MBMS, the Iub transmission bearer is used for transmitting data of aparticular multicast group or a particular MBMS service.

The TNL 521 of the base station 520 transfers the received DSCH dataframe to the DSCH FP 522. The DSCH FP 522 of the base station transfersthe DSCH transmission block and the DSCH control information included inthe received DSCH data frame, to the physical layer 523 of the basestation. The physical layer 523 of the base station uses the channelcodes included in the DSCH control information to transmit MBMS data tothe terminal via the PDSCH, which is a physical channel. Also, thechannel code data and the transmission format association data includedin the DSCH control information are transferred to the correspondingterminal group via the TFCI field of the associated DPCCH. If the TFCIfield of the PDSCH radio frame indicates that reception should be made,the terminal within the terminal group receives the corresponding PDSCHradio frame, performs decoding and then transfers a transmission blockto the MAC layer 533 of the terminal. The terminal MAC layer 532 removesthe MAC header from the corresponding MAC PDU, and transfers to the RLClayer 533 of the terminal via a CTCH. Accordingly, the data transmissionflow for a point-to-multipoint DSCH that includes an Iub region is shownby the arrows in FIG. 6. In the present invention, the CTCH can bereplaced by the MBMS traffic channel (MTCH).

The present invention provides in an embodiment thereof, a method ofproviding multicasting services to a plurality of users in radiocommunication, whereby the method comprises the steps of establishingthree or more data transmission states (e.g., States A, B, and C),employing two or more state transition conditions to change or maintainthe data transmission state, and providing data of the multicastingservice to the user with a particular data transmission state determinedby the state transition conditions.

Regarding the above method assuming there are three data transmissionstates, two of the states relate to a dedicated channel and theremaining state pertains to a forward access channel. In particular, ofthe two states that relate to a dedicated channel, one state is basedupon point-to-point data transmission, and the other state is based uponpoint-to-multipoint data transmission.

Also, one data transmission state can transition directly to anotherdata transmission state in accordance with the transition conditions. Inother words, in the above situation assuming three states (States A, B,and C), a transition can occur from State A “directly” to State B,without going through State C. Likewise, a transition can occur fromState A “directly” to State C, without going through State B.

Here, some examples of the transition conditions include a total numberof users, and parameters for radio communication resources. It can beunderstood that many other types of transition conditions may beemployed as desired.

FIG. 7 illustrates a state transition diagram when MBMS service isprovided via a FACH or a point-to-multipoint DSCH according to anembodiment of the present invention.

State 1 is the state where a point-to-multipoint MBMS radio bearerservice is provided via the FACH. Namely, logical channel CTCH data istransmitted via the FACH. Here, those terminals having a RRC connectioncan receive the CTCH data via the FACH when the terminal is in aCell_DCH, a Cell_FACH, a Cell_PCH, and a URA_PCH state.

State 2 is the state where a point-to-multipoint MBMS radio bearerservice is provided via the point-to-multipoint DSCH. For thoseterminals having a point-to-multipoint DSCH established thereto, a DCHis also established. Thus, only those terminals in a Cell_DCH state canreceive the point-to-multipoint DSCH. However, the DCH is not used intransmitting point-to-multipoint MBMS data.

State 3 is the state where a point-to-point MBMS radio bearer service isprovided via the DCH. This state is the same as the Cell_DCH state ofthe related art. If the number of users in a particular cell receivingthe MBMS is relatively small, the MBMS service is provided via a smallnumber of DCHs. Here, a point-to-point DSCH of the related art (which isdistinct from a point-to-multipoint DSCH) can be established togetherwith the DCH. A point-to-point DSCH, as in the related art, allowstransmission of data of an RLC entity such as a DCH, so the same MBMScan be transmitted via a DCH or a point-to-point DSCH.

The reasons why transitions from one state to another state occur willbe explained. Regarding transition A, the terminal in State 2 cantransition to State 1 if the transmission power required fortransmitting a particular MBMS is smaller than a particular thresholdvalue. In contrast, it is more advantageous with respect to transmissionpower usage for a terminal to transition from State 1 to State 2 if thetransmission power is larger than the particular threshold value.

For transition B, the terminal in State 2 can transition to State 3 ifthe number of terminals wishing to receive a particular MBMS is smallerthan a particular threshold value. In contrast, the terminal cantransition from State 3 to State 2 if the number of terminals is largerthan the particular threshold value. Also in transition B, the terminalin State 2 can transition to State 3 if the number of codes required fortransmitting a particular MBMS is smaller than a particular thresholdvalue. In contrast, the terminal can transition from State 3 to State 2if the number of codes is larger than the particular threshold value.This is because it is more advantageous with respect to the number ofcodes to be used, when the DSCH is employed.

Transition C can be performed for the same reasons as those forTransition B explained above. Namely, the terminal in State 1 cantransition to State 3 if the number of terminals wishing to receive aparticular MBMS is smaller than a particular threshold value. Incontrast, the terminal can transition from State 3 to State 1 if thenumber of terminals is larger than the particular threshold value. Alsoin transition C, the terminal in State 1 can transition to State 3 ifthe number of codes required for transmitting a particular MBMS issmaller than a particular threshold value. In contrast, the terminal cantransition from State 3 to State 1 if the number of codes is larger thanthe particular threshold value.

FIG. 8 illustrates a process of transmitting MBMS data via apoint-to-multipoint DSCH according to an embodiment of the presentinvention. Merely for the purpose of explaining this process, it isassumed that there are two terminals (Terminal #1 and Terminal #2)731,732 that receive a particular MBMS at a cell, and that the UTRANincludes two SRNCs (SRNC #1 and SRNC #2) 741,742 that manage thededicated resources (that are distinct from the MBMS) of the twoterminals.

Namely, SRNC #1 is for Terminal #1, and SRNC #2 is for Terminal #2. TheSRNC #1 and SRNC #2 transmit data to the base station and to eachterminal through a CRNC that is shared by the two terminals. The CRNChandles the transmission of MBMS data via a point-to-multipoint DSCH. Itshould be noted that the number of terminals and SRNCs might varyaccording to the desired communication environment, as would beunderstood by those skilled in the art. The process of transmitting MBMSdata via a point-to-multipoint DSCH is as follows:

1) Upon generation of MBMS data to be transmitted via thepoint-to-multipoint DSCH, the CRNC transmits to the base station, a MACPDU containing MBMS data and a DSCH data frame having TFI2 (transmissionformat indicator 2) data that is necessary for creating TFCI2(transmission format combination indicator) data. Here, TFI2 dataincludes PDSCH code data and DSCH transmission format data.

2) Distinct from the MBMS data transmission via the DSCH, the SRNC #1transmits dedicated data of the corresponding terminal and DCHtransmission format data (TFI1 data) to the base station.

3) Distinct from the MBMS data transmission via the DSCH, the SRNC #2transmits dedicated data of the corresponding terminal and DCHtransmission format data (TFI1 data) to the base station. Here, the twodifferent SRNCs (SRNC #1 and SRNC #2) can transmit respectivelydifferent dedicated data and TFI1 data.

4) The base station creates a TFCI from the TFI2 data transferred by theCRNC and from the TFI1 data transferred from the SRNC #1, which is thentransferred to Terminal #1 via DPCH #1 together with dedicated data.Here, the TFCI information of the DPCH comprises TFCI1 (that correspondsto the TFI1 data) and TFCI2 (that corresponds to the TFI2 data).

5) In the same manner, the base station creates a TFCI from the TFI2data transferred by the CRNC and from the TFI1 data transferred from theSRNC #2, which is then transferred to Terminal #2 via DPCH #2 togetherwith dedicated data. Here, the TFCI information of the DPCH comprisesTFCI1 (that corresponds to the TFI1 data) and TFCI2 (that corresponds tothe TFI2 data).

6) Terminal #1 and Terminal #2 receive the PDSCH data from the channelcode data of the TFCI2 data, and from the transmission format data. ThePDSCH channel allows transmission of the MBMS data.

Here, the base station must be able to recognize which terminal or whichDPCH is associated to the point-to-multipoint DSCH. This is because thebase station must transmit DSCH control information via the associatedDPCH. In the related art, only a single associated DPCH existed in onecell. However, to support the multicasting of data, the number ofassociated DPCHs must equal the number of terminals that receive theMBMS service. Accordingly, upon generation of MBMS data to betransmitted via the point-to-multipoint DSCH (in step 1) above) or priorto data transmission, the relationship between the point-to-multipointDSCH and the one or more associated DPCHs must be provided to the basestation.

To summarize, in order to overcome the problems in transmittingmulticast data via the DSCH according to the related art, the presentinvention proposes a radio (wireless) communication scheme where a RLClayer is provided in the CRNC. By using this scheme, the same servicedata can be transmitted to a plurality of terminals via the DSCH(referred to as a point-to-multipoint DSCH according to the presentinvention), yet the RLC layers required for the providing correspondingservices need not be repetitively provided in many SRNCs, but be simplyprovided in only the CRNC. As such, UTRAN resources can be efficientlyemployed in providing multimedia data services (such as MBMS) to aplurality of users (terminals).

II. Providing MBMS by Establishing Two New Physical Downlink Channels

The present invention provides in an embodiment thereof, a method forproviding a multimedia service in a radio communication system, themethod comprising, establishing a shared data channel and a sharedcontrol channel; and transmitting data of the multimedia service via theestablished shared data channel and the established shared controlchannel.

Here, the established channels are physical layer channels, whereby theshared data channel is for data only, while the shared control channelis for control and/or data.

According to the present invention, in a wireless system that broadcastsor multicasts a plurality of data services via a D-PDSCH (PhysicalDownlink Shared CHannel for Data) that can be received by a plurality ofterminals, the wireless system transmits data by varying the controlinformation of the D-PDSCH at each prescribed time period, and thevaried control information is transmitted via a C-PDSCH (PhysicalDownlink Shared CHannel for Control) that uses a different code than theD-PDSCH.

Here, the varied control information includes the channel codeinformation, channel coding information, or modulation information ofthe D-PDSCH, or the information that indicates to the terminal groupwhether the D-PDSCH should be received for a prescribed time period. Thechannel code information of the D-PDSCH refers to a channel code number,a SF of the channel code, and the number of channel codes used inmulti-code transmission.

The D-PDSCH according to the present invention allows transmission ofdata for a particular MBMS during a particular radio frame. Also,respectively different radio frames are allowed to carry respectivelydifferent MBMS data. Namely, a particular radio frame of the D-PDSCHrefers to the time period of reception for a particular terminal groupthat desires to receive the MBMS to be transmitted at that radio frame.The D-PDSCH is mapped to a downlink common shared channel, such as anFACH or DSCH.

The C-PDSCH of the present invention performs the function of allowingtransmission of control information necessary when each of the pluralityof terminals receives data being transmitted through the D-PDSCH.Namely, to allow a particular terminal group to receive the data of aparticular MBMS being transmitted during a particular radio frame of theD-PDSCH, control information must be transmitted (from the network)during a particular radio frame of the C-PDSCH.

The C-PDSCH of the present invention allows transmission of the controlinformation necessary for receiving the data of respectively differentMBMS during respectively different radio frames. Thus, the C-PDSCHcarries the control information needed for receiving the data for one ormore MBMS by one or more users.

The UTRAN manages a particular D-PDSCH and a particular C-PDSCH that isa counterpart (associated) thereto. The terminal group receiving data ofa particular MBMS, receives data on both a particular D-PDSCH and itscounterpart, a particular C-PDSCH.

The structure of the two new physical channels (D-PDSCH and C-PDSCH)will now be described in more detail. FIG. 9 shows the structure of aD-PDSCH according to the present invention. The D-PDSCH is a physicalchannel that is newly established to allow downlink transmission of datafor one or more MBMS, and permit one or more terminals to simultaneouslyreceive data thereof. The D-PDSCH is used to carry respectivelydifferent MBMS data by using the division of prescribed time periods.

Here, the prescribed time period is referred to as a radio frame, andone radio frame comprises one or more slots, as shown in FIG. 9. Theslot length is always constant, and one radio frame is comprised of anNd number of slots. Each slot comprises one field for transmitting data.

Although the D-PDSCH allows transmission by using one channel code, twoor more channel codes may be simultaneously used for transmission. Atransmission method of simultaneously employing two or more channelcodes is referred to as a multi-code transmission method. Multi-codetransmission is a transmission method especially applicable fortransmitting high-speed data by using a plurality of codes.

FIGS. 10A through 10E illustrate a structure of the C-PDSCH according toan embodiment of the present invention. The C-PDSCH is a newly createddownlink channel allowing more than one terminal to simultaneouslyreceive the control information of the D-PDSCH. The C-PDSCH is allowedto transmit variable control information by dividing the transmissionsinto prescribed time periods. Namely, the C-PDSCH allows datatransmissions by updating the control information upon dividing thetransmissions into certain time periods. Thus, the control informationcan be changed (varied) for each radio frame and then transmitted.

One radio frame comprises one or more slots. The slot length is alwaysconstant, and one radio frame comprises an Ns number of slots. In theC-PDSCH, one slot is comprised of one or more fields. One slot allowstransmission of one or more data, the data are included in the one ormore fields and then transmitted. The data and the fields that aretransmitted by each slot of the C-PDSCH will now be described in moredetail.

First, each slot may include a field that contains reception indicatordata, which indicates whether a terminal should receive a particularradio frame of the D-PDSCH.

Second, each slot may include a field that contains channel code data(e.g., channel code number, SF data of the channel code, the number ofchannel codes used in multi-code transmissions), which is used during aparticular radio frame of the D-PDSCH.

Third, each slot may include a field that contains pilot bits forestimating a condition of the radio channel at the receiving end.

Fourth, each slot may include a data field for service data transmittedby the D-PDSCH and for transmitting other services. The C-PDSCH allowstransmission of service data that the related art transport channels(FACH and RACH) can transmit. Also, using the data field of the C-PDSCH,establishment data of the D-PDSCH can be transmitted. Namely, after theterminal receives the establishment data of the D-PDSCH that istransmitted by the data field of the C-PDSCH, the establishment data isused by the terminal to establish that the D-PDSCH can be received.

Fifth, each slot may include a TFCI (Transport-Format CombinationIndicator) field. This field can include data regarding the number andsize of the data transmission block that is transmitted to the datafield of the C-PDSCH.

Each slot of the C-PDSCH may include all or any combination of theabove-identified fields. Also, among the types of data of theabove-identified fields, a portion thereof may be transmitted in onefield. If there are two or more fields being transmitted in the slot,the order of transmission is preferably determined in advance prior tothe design of the radio (wireless) network.

In particular, FIGS. 10A through 10E illustrate different forms of theradio frames for the C-PDSCH created by various exemplary embodimentsaccording to the present invention. Form A shows one slot that includesall five types of fields.

In contrast, as shown in Form B, the reception indicator field and achannel code field may be transmitted together via a single controlinformation field. Namely, each slot may include one field fortransmitting the control information of the D-PDSCH.

Also, as shown in Form C, control information may be transmittedtogether with the TFCI information within the same field. In otherwords, control information such as, reception indicator data and channelcode data may be transmitted together with the TFCI information in asingle field. Thus, the structure of Form C is the same as that of therelated art SCCPCH.

As shown in Form D and Form E, the reception indicator data or thechannel code data can be transmitted together with the TFCI informationin a single field. Here, channel code data or reception indicator datathat are not transmitted together with the TFCI information may betransmitted in an independent field.

FIG. 11 illustrates the time relationship between the C-PDSCH and theD-PDSCH. A particular radio frame of the C-PDSCH carries controlinformation for a particular radio frame of the D-PDSCH. Namely, theparticular radio frame of the C-PDSCH is an associate or a counterpart(complement) to the particular radio frame of the D-PDSCH.

The transmission side (e.g., UTRAN) transmits these radio frames havinga complementary (associated) relationship with a prescribed timeinterval (delay). In other words, the transmission side provides thatthe transmission starting point of the particular radio frame for theC-PDSCH and the transmission starting point of the particular radioframe for the D-PDSCH have a time delay amounting to the time intervalTsd. Accordingly, the radio frame of the C-PDSCH is always transmittedby the transmission side before the associated radio frame of theD-PDSCH, by the time interval Tsd.

The reception side (e.g., terminal) also receives the radio frame of theC-PDSCH first, and then after a time interval Tsd, the associated radioframe of the D-PDSCH is received. The Tsd value is determined by the RNCwhen the C-PDSCH and the D-PDSCH are established. The RNC transfers thedetermined Tsd value to the base station (Node-B) and the terminals (UE)when the channels are established. For the terminal, the RRC layer ofthe RNC (RNC RRC layer) first transfers the Tsd value to the RRC layerof the terminal (terminal RRC layer). Then, the terminal RRC layertransfers the received Tsd value to physical layer of the terminal. Theterminal can determine the associated relationship between the radioframe of the C-PDSCH and the radio frame of the D-PDSCH. Namely, theterminal decides that the radio frame of the C-PDSCH and the radio frameof the D-PDSCH, having a time interval of Tsd therebetween, have anassociated relationship.

If the TFCI field allows transmission of two or more data, as in FormsC, D and E in FIG. 5, the channel coding method of the TFCI division(partition) mode (mentioned in the related art) may be employed. Namely,respectively different bi-orthogonal code encoders are used for the twodata included in the TFCI field. In other words, in Form C, the TFCIinformation and the control information are channel encoded by usingrespectively different bi-orthogonal encoders. Also, in Form D, the TFCIinformation and the reception indicator data are channel encoded byusing respectively different bi-orthogonal encoders. In Form E, the TFCIinformation and the channel code data are channel encoded by usingrespectively different bi-orthogonal encoders.

FIG. 12 illustrates an example of the transmission and reception processof the C-PDSCH and the D-PDSCH according to the present invention. Here,the situations where the C-PDSCH is used to carry channel code data andreception indicator data of the D-PDSCH using two fields or one fieldwill be described. Namely, the control information includes the channelcode data and the reception indicator data of the D-PDSCH. Here, theterminal group refers to more than one terminal that receives particularMBMS data via the D-PDSCH. In the UTRAN, transmitting to the terminalgroup refers to broadcasting or multicasting.

1) The UTRAN transmits control information of the D-PDSCH via the radioframes of the C-PDSCH. The UTRAN, for each radio frame, transmitscontrol information of the D-PDSCH. If the reception indicator of thecontrol information indicates that the terminal should receive theassociated radio frame of the D-PDSCH, the physical layer of theterminal performs the following step. If the reception indicator of thecontrol information does not indicate that the associated radio frame ofthe D-PDSCH should be received, the physical layer of the terminal doesnot perform the following step, but receives the control information ofthe next radio frame.

2) If the reception indicator of the control information indicates thatthe associated radio frame of the D-PDSCH should be received, thephysical layer of the terminal, using the received channel code data ofthe control information, receives the data of the radio frame of theD-PDSCH which is associated to the radio frame of the C-PDSCH.

FIG. 13 illustrates a process of transmission and reception of theC-PDSCH and the D-PDSCH according to an embodiment of the presentinvention. Here, a radio frame of the C-PDSCH includes a data field, anda description of when the data field transmits establishment data of aD-PDSCH will be made. The terminal group refers to more than oneterminal that receives a particular MBMS data via the D-PDSCH. In theUTRAN, transmitting to the terminal group refers to broadcasting ormulticasting.

1) The RRC layer of the UTRAN transmits D-PDSCH establishment data tothe RRC layer of the terminal via lower layer services. Here, the datafield of the C-PDSCH transmits the establishment data of the D-PDSCH.

2) The terminal RRC layer forwards the received D-PDSCH establishmentdata to the lower layers of the terminal, and establishes itself toreceive the D-PDSCH.

3) The UTRAN transmits the control information of the D-PDSCH via theradio frame of the C-PDSCH. The UTRAN transmits the control informationof the D-PDSCH at each and every frame. If the reception indicator ofthe control information indicates that the terminal should receive theassociated radio frame of the D-PDSCH, the physical layer of theterminal performs the following step. If the reception indicator of thecontrol information does not indicate that the associated radio frame ofthe D-PDSCH should be received, the physical layer of the terminal doesnot perform the following step, but receives the control information ofthe next radio frame.

4) If the reception indicator of the control information indicates thatthe associated radio frame of the D-PDSCH should be received, thephysical layer of the terminal, using the received channel code data ofthe control information, receives the data of the radio frame of theD-PDSCH which is associated to the radio frame of the C-PDSCH.

As described above, in providing various MBMS data to terminals (UE)within a cell via a FACH or a DSCH using the related art methods, thetransmission power required for providing even one data service (MBMS)occupies a large portion of the overall base station (Node-B in UMTS)power, because the FACH uses discontinuous transmissions, while the DSCHcarries control information via an exclusive physical channel.

Accordingly, the present invention employs a variable spreading methodusing a variable SF, instead of a discontinuous transmission method, torestrict the D-PDSCH. Also, a C-PDSCH, which is not a downlink exclusivephysical channel, is used as the channel for carrying controlinformation of the D-PDSCH. By doing so, the data transmissionefficiency for data services, such as MBMS is improved.

It can be understood that the present invention has been described inthe context of providing MBMS to users for exemplary purposes only.Thus, the teachings and/or suggestions of the present invention may alsobe applicable to other types of signal transmissions or data transfersthat should be provided to a plurality of users.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present invention.Accordingly, it is intended that the present invention covers themodifications and variations of this invention provided they come withinthe scope of the appended claims and their equivalents.

1. A method of providing a broadcast or multicast service, the method comprising: transmitting control information via a second downlink common physical channel such that at least one terminal is able to receive data of the broadcast or multicast service which is transmitted via a first downlink common physical channel; and transmitting the data of the broadcast or multicast service via the first downlink common physical channel, wherein the second downlink common physical channel comprises at least one of a TFCI (Transport Format Combination Indicator) field and a Pilot field to transmit the control information, wherein the second downlink common physical channel carries data of a service transmitted from an upper layer via a transport channel and which is different from the transmitted data of the broadcast or multicast service, and wherein the first downlink common physical channel and the second downlink common physical channel are mapped to the transport channel, the transport channel being a forward access channel (FACH).
 2. The method of claim 1, wherein the first downlink common physical channel is a downlink common data physical channel.
 3. The method of claim 1, wherein the second downlink common physical channel is a downlink common control physical channel.
 4. The method of claim 1, wherein the transmitted data of the broadcast or multicast service via the first downlink common physical channel is used by a plurality of codes.
 5. The method of claim 1, wherein the control information transmitted via the second downlink common physical channel comprises at least one of a receiving indicator field and a channel code field.
 6. The method of claim 1, wherein the control information transmitted via the second downlink common physical channel further comprises a receiving indicator field and a channel code field.
 7. A method of receiving a broadcast or multicast service, the method comprising: receiving in a terminal control information via a second downlink common physical channel to receive data of the broadcast or multicast service which is received via a first downlink common physical channel from a network; and receiving in the terminal the data of the broadcast or multicast service via the first downlink common physical channel, wherein the second downlink common physical channel comprises at least one of a TFCI (Transport Format Combination Indicator) field and a Pilot field to transmit the control information, wherein the second downlink common physical channel carries data of a service to be received by an upper layer via a transport channel, and which is different from the received data of the broadcast or multicast service, and wherein the first downlink common physical channel and the second downlink common physical channel are mapped to the transport channel, the transport channel being a forward access channel (FACH).
 8. The method of claim 7, wherein the first downlink common physical channel is a downlink common data physical channel.
 9. The method of claim 7, wherein the second downlink common physical channel is a downlink common control physical channel.
 10. The method of claim 7, wherein the received data of the broadcast or multicast service via the first downlink common physical channel is used by a plurality of codes.
 11. The method of claim 7, wherein the control information received via the second downlink common physical channel comprises at least one of a receiving indicator field and a channel code field.
 12. The method of claim 7, wherein the control information received via the second downlink common physical channel further comprises a receiving indicator field and a channel code field. 